The present invention relates to terminal clamp assemblies for clamping one or two wires, including pairs of wires of different size, to a terminal member. Such terminal clamp assemblies commonly include a screw and a clamp plate loosely mounted on the screw shank for tilting or teetering relative to the shank to accommodate wires of different size. In order to enhance the clamping action on wires of relatively different size, it has heretofore been proposed as disclosed in U.S. Pat. No. 3,891,296 to provide a circular protrusion on the underside of the head of the screw and a raised frusto-conical surface on the upper side of the clamp plate engageable with the circular protrusion on the head in different tilted positions of the clamp plate. The clamp plate in that patent, however, also had a generally frusto-conical depression in the underside of the clamp plate, produced as a consequence of forming the raised frusto-conical surface on the upper side of the clamp plate. In order to overcome the problem of delayed lifting of the clamp plate during unthreading of the screw, caused by the frusto-conical recess in the underside of the clamp plate, the frusto-conical portion of the clamp plate was flattened in four narrow areas to form inwardly extending ribs arranged to engage a collar on the shank of the screw and lift the clamp plate when the screw was unthreaded. However, these four narrow ribs sometimes tended to tilt or bind on the collar on the shank of the screw, unless the collar was made very large. The terminal clamp assemblies are commonly installed by automatic machinery in the terminal boards and the terminal boards frequently have a large number of terminal clamp assemblies thereon. Even one faulty terminal clamp assembly can make the terminal board unfit for use and such terminal boards containing a faulty terminal clamp assembly had to be either discarded or set aside and manually reworked to correct the defective terminal clamp assembly.
The clamp plate shown in Pat. 3,891,296, also required very substantial material movement in order to form the frusto-conical raised surface on the upper side of the clamp plate for engagement with the protrusion on the head of the screw, and to also form the inwardly extending ribs at the underside of the clamp plate for engagement with the collar on the shank of the screw. The amount of material movement required in forming the clamp plate in the aforementioned patent adversely affected die life. In addition, there was some shearing or tearing of the clamp plate at the junctures between the ribs and frusto-conical sections and which reduced the strength of the clamp plate.